From 30efa292790dfdc9eedefa97a9f82e1cac2aeaa0 Mon Sep 17 00:00:00 2001
From: sanine <sanine.not@pm.me>
Date: Fri, 24 Oct 2025 12:44:06 -0500
Subject: add alloc/dealloc functions for generic linked list

---
 lichen.c      | 34 ++++++++++++++++++++++++++++++++++
 lichen.h      | 27 ++++++++++++++++++++++++++-
 lichen.test.c | 27 +++++++++++++++++++++++++++
 3 files changed, 87 insertions(+), 1 deletion(-)

diff --git a/lichen.c b/lichen.c
index f20c1b3..e8c8e19 100644
--- a/lichen.c
+++ b/lichen.c
@@ -1,4 +1,6 @@
 #include "lichen.h"
+#include <stdio.h>
+#include <string.h>
 
 
 void li_xorshift32_seed(struct li_xorshift32_t *xor, uint32_t seed) {
@@ -18,3 +20,35 @@ uint32_t li_xorshift32(void *s) {
   // return just top 32 bits
   return x >> 32;
 }
+
+
+
+li_llnode_t * li_alloc_llnode() {
+  li_llnode_t *n = malloc(sizeof(li_llnode_t));
+  if (n == NULL) {
+    fprintf(stderr, "failed to allocate linked-list node\n");
+    return NULL;
+  } else {
+    n->tag = 0;
+    n->data = 0;
+    n->next = NULL;
+    return n;
+  }
+}
+
+
+li_llnode_t * li_copy_llnode(li_llnode_t *n) {
+  li_llnode_t *m = li_alloc_llnode();
+  if (m == NULL) {
+    return NULL;
+  }
+  memcpy(m, n, sizeof(li_llnode_t));
+  return m;
+}
+
+void li_free_llnode(li_llnode_t *n, void (*free_data)(void*)) {
+  if (n != NULL) {
+    free_data(n->data);
+  }
+  free(n);
+}
diff --git a/lichen.h b/lichen.h
index fe68d52..b30c8cb 100644
--- a/lichen.h
+++ b/lichen.h
@@ -1,9 +1,10 @@
 #ifndef LICHEN_H
 #define LICHEN_H
 
+#include <stdlib.h>
 #include <stdint.h>
 
-// random number generation
+/* --===== random number generation =====-- */
 typedef struct li_rand32_t {
   uint32_t (*rand)(void *);
   void *state;
@@ -21,4 +22,28 @@ void li_xorshift32_seed(struct li_xorshift32_t *xor, uint32_t seed);
 uint32_t li_xorshift32(void *s);
 
 
+/* --===== generic linked lists =====-- */
+
+
+typedef struct li_llnode_t {
+  int tag;
+  void *data;
+  struct li_llnode_t *next;
+} li_llnode_t;
+
+
+li_llnode_t * li_alloc_llnode();
+li_llnode_t * li_copy_llnode(li_llnode_t *n);
+void li_free_llnode(li_llnode_t *n, void (*free_data)(void*));
+
+
+typedef struct li_ll_t {
+  int tag;
+  size_t count;
+  li_llnode_t *head;
+} li_ll_t;
+
+
+
+
 #endif
diff --git a/lichen.test.c b/lichen.test.c
index 77ff067..68d26d0 100644
--- a/lichen.test.c
+++ b/lichen.test.c
@@ -24,6 +24,33 @@ LILY_TEST("xorshift output") {
 }
 #include LILY_PUSH_TEST()
 
+
+
+void do_nothing(void *k) {
+  k = k;
+}
+void free_data(void *m) {
+  li_free_llnode(m, do_nothing);
+}
+
+LILY_TEST("allocate, copy, and destroy llnode") {
+  li_llnode_t *n = li_alloc_llnode();
+  REQUIRE_NEQ(n, NULL, "%p");
+  CHECK_EQ(n->next, NULL, "%p");
+  int k = 0;
+  n->tag = 4;
+  n->data = &k;
+  li_llnode_t *m = li_copy_llnode(n);
+  REQUIRE_NEQ(m, NULL, "%p");
+  CHECK_EQ(m->tag, 4, "%d");
+  CHECK_EQ(m->data, &k, "%p");
+  CHECK_EQ(m->next, n->next, "%p");
+  n->data = m;
+  li_free_llnode(n, free_data);
+}
+#include LILY_PUSH_TEST()
+
+
 #define LILY_FILE_END
 #include LILY_REGISTER_TESTS()
 
-- 
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